The invention relates to diesel particulate collectors for controlling exhaust emissions from a diesel internal combustion engine.
In the control of diesel particulate emissions, wall flow filters have been widely used. The restriction of the filter increases with time due to the increasing amount of soot deposited in the filter. The limited soot loading capacity requires the filter to be regenerated through either passive or active processes. During each cycle of regeneration, however, a filter can never be recovered to its initial restriction level due to ash accumulation. A filter has to be discarded if it cannot be regenerated to meet back pressure requirements specified by the diesel engine manufacturer. A system with high soot loading capacity is thus desired, for less frequent regeneration, longer operating time, and longer service intervals.
The present invention provides a multi-stage diesel particulate collector combining in preferred form various principles including inertial impaction, virtual impaction, and filtration. A series of inertial impactors form a cascade to trap diesel soot particles. The inertial impactor accelerates the particle laden exhaust gas flow through an array of orifices or nozzles, and then forces the flow to change direction, causing the larger particles to impact on a collector. Low pressure behind the porous impactor generates secondary flow causing smaller soot particles to be virtually impacted and then captured through a filtration process. As the flow moves through further stages, even smaller particles are carried with the exhaust gas flow stream and are removed at following stages of collectors.